1. Field of the Invention
The present invention relates to a semiconductor device and a technique for producing the same, and for example, relates to a technique effectively applied to a semiconductor device including a power device constituting an inverter and a technique for producing the same.
2. Background Art
For example, as disclosed in NPL 1 (J. Kedzierski, et al., “Complementary silicide source/drain thin-body MOSFETs for the 20 nm gate length regime”, Tech. Dig. IEDM 2000, pp. 57-60), as a method for forming a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) without resort to high-temperature activation in a silicon semiconductor, a Schottky barrier MOSFET (Schottky Barrier Transistor, hereinafter referred to as “SBT”) using a metal material as it is as a material for a diffusion layer electrode such as a source region or a drain region is known.
Recently, in order to achieve low-carbon society, more highly efficient use of energy has become an important and urgent issue. In order to highly efficiently use energy, an effect of reducing power loss in an inverter can contribute thereto, and therefore, the development of a power device constituting an inverter is important. Under the research and development in this manner, as a material for a power MOSFET, replacement of Si (silicon) to SiC (silicon carbide) has been under consideration. This is because as compared with Si (silicon) SiC (silicon carbide) has about 7 times higher dielectric breakdown field strength and about 3 times larger band gap, and therefore has characteristics that it can reduce loss and allow high-temperature operation of power devices. Hereinafter “silicon” and “silicon carbide” are sometimes referred to as “Si” and “SiC”, respectively.
A SiC power MOSFET can decrease the on-resistance as compared with a Si power MOSFET in the case where the voltage resistance is equivalent. This is attributed to the fact that the thickness of an epitaxial layer serving as a drift layer can be decreased when using SiC as compared with Si. However, in consideration of commercialization of a product as a practical industrial device, as compared with silicon devices having been established as the advancement of LSI (Large-Scale Integration) since around 1960 and the production process thereof, SiC devices still have a lot of problems.
For example, a SiC power MOSFET is known to have a problem that the channel mobility is decreased. As compared with Si (silicon), SiC (silicon carbide) has a higher dielectric breakdown field strength and a larger band gap, and therefore, the thickness of a drift layer (an epitaxial layer) for ensuring the voltage resistance can be decreased. As a result, the thickness of the drift layer having a low impurity concentration is decreased, and therefore, the on-resistance can be decreased. On the other hand, in the SiC power MOSFET, the channel mobility is decreased. Therefore, if the channel mobility can be increased in the SiC power MOSFET, the on-resistance can be further decreased. That is, in the SiC power MOSFET, due to the fact that as compared with Si, SiC to be used as a substrate material has a higher dielectric breakdown field strength and a larger band gap, if the voltage resistance is equivalent, the on-resistance can be decreased, however, in addition thereto, if the channel mobility can be increased, the on-resistance can be further decreased. In view of this, from the viewpoint of aiming at reduction of on-resistance, the SiC power MOSFET still has room for improvement, and by the reduction of on-resistance, there is a possibility that a SiC power MOSFET having high performance can be realized.